There are many different types of working fluids—fluids that are used primarily to reduce and/or convey energy such as heat and/or to convey matter such as a chemical, molecule and/or an arrangement of molecules from one place to another in a system. The type of fluid used as a working fluid in a system often depends on the specific requirements of the system. For example, oil in an engine is desired because it can withstand a moderate amount of heat and lubricates many moving parts within the engine to reduce the amount of unwanted heat generated by the engine.
Water is another type of working fluid and is often used in systems to convey heat and/or matter within the system. For example, water is often used to remove from a system excess heat generated in the system. In such uses, the water flows through a heat exchanger of the system where it absorbs heat from the system. The heated water then flows to another heat exchanger—often a cooling tower—to release its heat to the ambient environment. A cooling tower works by directing ambient air through a flow of water droplets. As the air contacts the water droplets, some of the water's heat is removed from the water via convection, and some of the water's heat is removed from the water via evaporation. Consequently, water must be routinely added to the system to replace the water lost from evaporation.
Unfortunately, the water of such systems must also be routinely treated to maintain a desired hardness. Hardness is a measure of the amount of cations—positively charged atoms or molecules—in the water, which are usually caused by dissolved metals. The larger the number of cations or amount of dissolved metals in the water, the harder the water. The two most common metals that contribute to water's hardness are calcium (Ca) and Magnesium (Mg). These metals typically exist as carbonate molecules CaCO3 and MgCO3 that when dissolved in water yield Ca+2, Mg+2, and CO3−2. Because water that evaporates does not include the metals, and thus the cations, and because water that is added to the system typically does include such metals, the hardness of the water or working fluid of the system increases over time. This increase can lead to excessive hardness in the water which can cause scaling in the system which can foul components of the system like pipes, valves and pressure sensors. Excessive hardness in the water or working fluid can also promote corrosion in the system, causing premature and possibly catastrophic failure.
One method for reducing the hardness of the water in such systems is to simply dump a large portion of the water out of the system and replace the dumped water with water whose hardness levels are less than the levels of the dumped water. Unfortunately, this consumes much water because the amount of water needed to replace the dumped water can be large, and the frequency at which the dump and replacement should occur can be high. Also, the water that is dumped is too contaminated to be readily used for something else. To reduce the amount of water dumped and the frequency at which the dump occurs, many chemically treat the water to keep the minerals in a less destructive form. Unfortunately though, chemically treating the water doesn't allow one to avoid having to periodically dump the water because the water and the chemical program have limits to the amount of minerals and chemicals that they can hold.
Thus, there is a need for a system that more efficiently removes unwanted minerals and other unwanted chemicals from a working fluid such as water in a cooling tower system.